The Galileo Open Service Signal In Space Interface Control Document (OS SIS-ICD) was posted on May 2006 and reviewed in Septembre 2010. It specifies the interface between the Galileo Space Segment and the Galileo User Segment and defines the signals and services that will be transmitted at E1, E5, and E6 frequencies (the spreading codes, the navigation message format, etc.). This information is vital for GNSS receiver designers and manufacturers in order to build Galileo receivers.

[Galileo Open Service Signal in Space ICD (pdf)]